1. Field of the Invention
The present invention generally relates to slide fastener chain that includes fabric and features that allow the zipper tapes to stretch in the lateral direction. Slide fastener chain is the combination of two slide fastener tapes and fastener elements mounted thereon, and that is manufactured in bulk lengths. A slide fastener assembly, or zipper, is made by cutting a desired length of chain, mounting a slider assembly, and optionally adding top and/or bottom stops, pin boxes, etc.
There are a number of applications for slide fasteners that incorporate tapes that can stretch, such as clothing, luggage, and footwear. A conventional zipper must be very stable in the longitudinal direction (along its length) in order that the teeth of the opposing tapes properly engage, and are generally also very stable in the lateral direction (across its width). A zipper that can stretch in the lateral direction, but be stable in the longitudinal direction, is less likely to fail due to the teeth becoming disengaged when closed because the fabric tape can absorb some of the stress that would otherwise bear on the teeth. The use of such a zipper is desirable in luggage as it makes it easier to close the zipper on a fully loaded or overloaded bag. Such a zipper can also be used in applications where some amount of give is desirable even if the lateral stress is minimal, such as a dress. In one application, slide fasteners made from tapes of the present invention are used as a closure for luggage. In other applications such zippers may be use for garments such as pants or dresses. Other applications include zippers for the sides of tall form-fitting boots.
There have been many attempts at making a zipper with tapes that allow for significant lateral stretch. There have been some such zipper products that have had modest success in the marketplace, but these products have suffered from poor performance due to inadequate stretch (in proportion to the tape width), lack of rebound (the ability of the tape to quickly and repeatedly return to its non-stretched width), and lack of durability. A need exists for improvement in the field of stretchable slide fastener chain that address the shortcomings of the prior art, and from which stretchable slide fastener assemblies (zippers) may be made. This and other needs are addressed by one or more aspects of the present invention.
2. Description of Related Art
There are numerous means for making a zipper stretchable in the lateral direction by using fabric tapes that are made from stretchable weaving yarns. While such fabrics are readily available, they are not suitable for use in a zipper unless the tape is stable (non-stretchable) in the longitudinal direction (the length of the zipper from pin box to top-stop for instance). In order to weave a zipper tape, the warp weaving yarns are aligned in the longitudinal direction, and the weft weaving yarns are aligned perpendicular to the warp yarns. Since any stretch in the longitudinal direction of the zipper would allow the zipper teeth of a finished zipper assembly to become disengaged, extremely stable (no longitudinal stretch) warp weaving yarns are required. The challenge in producing a zipper tape that stretches in the direction of the weft weaving yarns is to use weaving yarns that have nominal, repeatable stretch. Excessive stretch in the lateral direction can create performance issues that interfere with the proper movement of the zipper slider and can result in dislocations between opposing fastener elements (teeth).
Stretchable tapes have been made using a variety of stretchable weft weaving yarns that include stretchable fibers such as spandex. However, tapes of the prior art that use stretchable fibers do not exhibit sufficient stretch (in terms of the ratio of the stretched width to the un-stretched width of the tape), or are not durable due to failure of the stretchable weft weaving yarns (during weaving, or during use due to physical abrasion or laundering or drying heat), or loss of stretch memory (the ability of the stretched tape to return to the original un-stretched tape width quickly and repeatedly). Therefore, it is an objective of the present invention to create a slide fastener using fabric tapes that have the desired stretch characteristics (ratio of stretched to un-stretched tape width) and acceptable durability.
The slide fastener chain and tapes of the present invention provides for a sufficient degree of stretchability and durability.